Brendan J. Kelly, M.D., M.S., studies infectious diseases and epidemiology at the University of Pennsylvania. His research focuses on microbial ecosystems in humans at high risk for infection. Dr. Kelly seeks to understand properties of microbial ecosystems that protect against infection, how microbial ecosystems are altered by antibiotics, and how microbial ecosystems recover from infection and antibiotic treatment. He has performed large, clinical-translational studies to better understand pneumonia and intestinal infections that occur in the setting of critical illness. Dr. Kelly’s work has been supported by the National Institute of Allergy and Infectious Diseases (NIAID) and the Centers for Diseases Control and Prevention (CDC).